The present invention relates to a machine for cutting the cylindrical wall of tamper-evident plastic caps in order to form a fracture line which is suitable to facilitate the separation of a tamper-evident ring during the removal of the cap from the container to which it has been applied.
Plastic caps are known which are provided with a tamper-evident ring, i.e., with a ring which is fixed below the cup of the cap by means of bridges which break during the initial unscrewing of the cap and allow to determine whether the cap has been tampered with or not.
In some types of cap, the tamper-evident ring and the corresponding bridges for coupling to the cup are obtained by molding together with the cap itself.
In other types, the ring is molded monolithically with the cup and is rendered separate from said cup at a later stage by means of peripheral cuts, so that the tamper-evident ring remains attached to the cap only with very short intact portions which constitute said bridges.
In some conventional machines, the cuts in the cylindrical wall of the cup are performed by means of a cutter with a circular cutting edge, against which the caps are rolled. A plurality of appropriately spaced notches are formed in the cutting edge and form the bridges.
These conventional machines suffer the drawback that replacing the cutter, for example due to wear or breakage or due to requirements imposed by the structure of the cap, is a highly complex and time-consuming operation.
The aim of the present invention is to obviate the above-cited drawbacks of conventional machines, by providing a machine for cutting tamper-evident rings which does not wear and can be easily adapted to different cutting methods and to different cap shapes.
Within the scope of this aim, an object of the present invention is to achieve the above aim by providing a machine which is simple, relatively easy to manufacture, safe in use, effective in operation, and relatively modest in cost.
This aim and this object are both achieved by the present machine for cutting the cylindrical wall of the cup of plastic caps in order to form a fracture line which is suitable to facilitate the separation of a tamper-evident ring, characterized in that it comprises at least one cap support which rotates about an axis, and a laser beam emitter arranged, with respect to said support, so that said beam strikes said cylindrical wall of the cap, said emitter being activated and deactivated in accordance with the rotary motion of the cap, so as to form in the cylindrical wall of the cap a plurality of cuts alternated with short intact portions, which form a fracture line allowing the separation of said tamper-evident ring from said cup.